IV Drip Rate Calculator
Drip rate
– gtt/min
Enter a volume and a time.
- Seconds between drops
- –
- Equivalent pump rate
- –
The working
This works out the arithmetic. The order, the product in your hand and local policy still govern what is given.
The drip rate formula
gtt/min = volume in mL × drop factor in gtt/mL ÷ time in minutes
The time goes in as minutes, so an infusion written in hours is multiplied by 60 first. The answer is rounded to whole drops, because drops are counted rather than measured.
Checking it at the bedside is easier with the seconds between drops than with the rate itself. At 31 gtt/min a drop falls roughly every two seconds, which is a count you can do against a watch without waiting a full minute.
Drop factors and why the set matters
One litre over eight hours, through each of the standard giving sets:
| Giving set | Drop factor | Drip rate | Used for |
|---|---|---|---|
| Macrodrip | 10 gtt/mL | 21 gtt/min | Macrodrip, blood giving set |
| Macrodrip | 15 gtt/mL | 31 gtt/min | Macrodrip, common standard set |
| Macrodrip | 20 gtt/mL | 42 gtt/min | Macrodrip, common standard set |
| Microdrip | 60 gtt/mL | 125 gtt/min | Microdrip, paediatric and low-volume sets |
Same bag, same eight hours, four different counts. The fluid delivered is identical in every row; only the number of drops it arrives in changes. Taking the drop factor from memory rather than from the packet is the way this calculation goes wrong.
Drip rate and pump rate
A pump is programmed in millilitres an hour and counts nothing, so the drop factor is irrelevant to it. A gravity line is counted in drops a minute and needs it. The two describe the same flow, which is why the calculator shows the equivalent pump rate alongside the drop count.
For a pump, the IV flow rate calculator gives mL/hr directly, and theinfusion time calculator answers how long a bag will last at a rate that is already running.
Questions about drip rates
- What is the formula for IV drip rate?
- Drops per minute equals the volume in mL multiplied by the drop factor in gtt/mL, divided by the time in minutes. The drop factor comes from the giving set packaging.
- What is a drop factor?
- How many drops of fluid it takes that particular giving set to deliver one millilitre. Standard macrodrip sets are 10, 15 or 20 gtt/mL; microdrip sets are 60 gtt/mL. It is a property of the tubing, so it has to be read rather than assumed.
- What is the difference between macrodrip and microdrip?
- A macrodrip set delivers larger drops and is used for routine volumes. A microdrip set delivers 60 small drops per millilitre, which gives finer control at low rates and is used for paediatric and low-volume infusions.
- Do you round drip rate up or down?
- To the nearest whole drop, because a fraction of a drop cannot be counted. The rounding changes the delivered rate slightly, which matters more on a microdrip set at a low rate than on a macrodrip set at a high one.